A spatial study of the mid-IR emission features in four Herbig Ae/Be stars

被引:22
作者
Boersma, C. [1 ]
Peeters, E. [2 ,3 ,4 ]
Martin-Hernandez, N. L. [5 ]
van der Wolk, G. [1 ]
Verhoeff, A. P. [6 ]
Tielens, A. G. G. M. [4 ]
Waters, L. B. F. M. [6 ]
Pel, J. W. [1 ]
机构
[1] Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands
[2] Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada
[3] SETI Inst, Mountain View, CA 94043 USA
[4] NASA, Ames Res Ctr, Moffett Field, CA 94035 USA
[5] Inst Astrofis Canarias, E-38205 San Cristobal la Laguna, Spain
[6] Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands
关键词
techniques: spectroscopic; infrared: ISM; ISM: molecules; astrochemistry; POLYCYCLIC AROMATIC-HYDROCARBONS; CIRCUMSTELLAR DUST; ISO SPECTROSCOPY; PAH EMISSION; INFRARED-EMISSION; HII-REGIONS; AE STARS; AB AUR; SPECTRA; MULTIWAVELENGTH;
D O I
10.1051/0004-6361/200911820
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Context. Infrared (IR) spectroscopy and imaging provide a prime tool to study the characteristics of polycyclic aromatic hydrocarbon (PAH) molecules and the mineralogy in regions of star formation. Herbig Ae/Be stars are known to have varying amounts of natal cloud material present in their vicinity. Aims. Our aim is to study the characteristics of the mid-IR emission originating in Herbig Ae/Be stars, especially the extent of the emission and how this relates to the (proto-) stellar characteristics. Methods. Today's powerful ground-and space-based telescopes provide images and spectra at unprecedented spectral and spatial resolution. We analyse the images and spectra from four Herbig Ae/Be stars (IRAS 06084-0611, CD-42 11721, TY CrA, and HD176386), as obtained with TIMMI2 on the ESO 3.6 m telescope and VISIR on the VLT. These observations are supplemented with data from ISO-SWS and Spitzer-IRAC. Results. We find evidence for large-scale structure and extended emission in all four sources, except for HD176386, which only shows silicate emission, all sources show PAH emission in their spectra. In addition, a spatially resolved silicate and PAH spectrum could be extracted for TY CrA. Conclusions. The variety in emission scales distinguishes two classes. In the first, the morphology and spectral characteristics resemble those of reflection nebulae. In the second, the characteristics are in-line with Herbig A stars. This separation simply reflects a difference in stellar characteristics (e. g. luminosity). In Herbig B stars, dust emission from the surroundings dominates, where for Herbig A stars, the disk dominates the emission. In this scheme, IRAS 06084-0611 and CD-42 11721 resemble reflection nebulae and HD176386 a more typical Herbig Ae/Be star. TY CrA shows characteristics common to both genuine reflection nebulae and Herbig B stars. We propose a geometry for TY CrA, with most notably, a similar to 70 AU inner gap in the 340 AU circumtertiary disk cleared by a fourth stellar companion.
引用
收藏
页码:175 / 187
页数:13
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